Efficacy of four insecticides on different types of storage bags for the management of Trogoderma granarium Everts (Coleoptera: Dermestidae) adults and larvae

The khapra beetle, Trogoderma granarium Everts (Coloeptera: Dermestidae), is a globally serious pest of several agricultural stored-commodities. Among new methods that target to control this species is the insecticidal treatment of storage bags. In the present study, we tested the efficiency of alpha-cypermethrin (= α-cypermethrin), chlorfenapyr, deltamethrin and pirimiphos-methyl applied on woven polypropylene, biaxially oriented polypropylene and kraft paper storage bags against adults and larvae of T. granarium under three treatment scenarios: one surface of the storage bag was treated and individuals were exposed on treated or untreated surface or both surfaces were treated. We estimated the immediate mortality after 1, 3 and 5 days (d) of exposure. Then, we placed adults and larvae that were alive unto untreated surfaces of the same type of storage bags and evaluated the delayed mortality after 7 d of exposure. Regarding immediate mortality, the most effective insecticides were chlorfenapyr and pirimiphos-methyl against both life stages. All insecticidal combinations resulted in very high delayed mortality values that finally killed ≥91.1% of the initially exposed adult population of T. granarium while in several combinations all adults died due to the delayed mortality. The initial population of T. granarium larvae was further reduced through delayed mortality, but there were still alive individuals on the storage bags. In the majority of combinations with α-cypermethrin, deltamethrin and pirimiphos-methyl, there were no significant differences in the mortality levels of adults and larvae when they were exposed onto the treated surface of the storage bags having one or both surfaces treated. All insecticides performed equally on the three tested types of storage bags. The present study illustrates that the application of chlorfenapyr and pirimiphos-methyl on different types of storage bags could be considered as additional tools for the management and regulation of expansion of T. granarium.